One of the most common sources of information about a country is the country's statistical agency. In Canada, we are used to going to the Statistics Canada website for information about our country. The best way to find a country's statistical agency is to Google "X country statistics". Note, there may not be an English version available. Unless you are able to speak the language, this may pose a barrier to using this as a primary source. For example, if I wanted to choose Cuba for my assignment, I couldn't use data from their statistics office unless I speak Spanish.
Another consideration is how trustworthy the available statistics may be. Depending on the type of government in the country of choice, there could be some concerns with the reliability of the data. There may be a reduced transparency in data collection methods, or inconsistencies in the availability of data over time. Note that Canada is not exempt from this critique! The Harper government famously made a change to the way that our long-form census data was collected in 2011. As a result, there will be an enduring gap in knowledge about our country during this time.
Alternative sources of information that are held up to rigorous standards are available via the following agencies:
UNICEF (United Nations International Children’s Emergency Fund)
UNESCO (United Nations Educational, Scientific and Cultural Organization) Digital Library
WHO (World Health Organization)